The first half of 2021 brought plenty of big stories that impacted healthcare stocks -- from COVID-19 vaccines' success to pivotal decisions from the U.S. Food and Drug Administration (FDA). In this Motley Fool Live video recorded on July 7, Motley Fool contributors Keith Speights and Brian Orelli talk about four large-cap healthcare stocks for investors to have on their radar in the second half of the year.

Keith Speights: Brian, we have moved past the first half of 2021 now, we're into the second half of the year. Are there any large-cap healthcare stocks that you think investors should have on their radar for the second half of this year?

Brian Orelli: Yeah, I'm definitely watching Biogen (NASDAQ:BIIB) and looking at the initial sales of Aduhelm, its new Alzheimer's disease drug. Then also looking at how quickly the decline of its multiple sclerosis drugs happens. Can Aduhelm make up the difference for the decline in multiple sclerosis drugs?

I'm looking at Moderna (NASDAQ:MRNA). It's crazy that's considered a large cap. But its market cap is actually substantially larger than Biogen's, it's at $93 billion last time I looked versus $52 billion for Biogen. Obviously, the main valuation driver for Moderna is going to be sales commitments for 2022 of its COVID-19 vaccine.

Then maybe a twofer -- AbbVie (NYSE:ABBV) and Pfizer (NYSE:PFE) for the outcome of the JAK inhibitor saga. There's probably other companies that are also involved in the issue. AbbVie's trying to get expanded use over Rinvoq, and then Pfizer has Xeljanz, which caused the controversy, and also abrocitinib.

I think seeing what the FDA outcome of looking at the Xeljanz data that showed that there were some safety issues with JAK inhibitors in whether the FDA says that it's a class issue. Then that would cause problems for AbbVie, as well as Pfizer's other JAK inhibitor.

Speights: All right. Brian, so you mentioned Biogen, Moderna, AbbVie, and Pfizer. Out of those four stocks, put on your prediction cap here. Which do you think would perform the best over the second half of this year?

Orelli: I want to go with Pfizer, I guess. [laughs] I've been saying this for a year and a half, Moderna's overpriced. [laughs] I've been wrong so far, so maybe I go with Moderna. But I feel like Pfizer is a value stock. That would probably be my best bet.

Biogen certainly could rocket higher, but I don't have confidence in Aduhelm. But I think there could be a lot of demand from patients, even if doctors aren't really interested in it. Maybe they succumb to the patient's desire to have the drug, and so maybe Biogen could rocket higher if Aduhelm sales are definitely well and do well.

Speights: Yeah, I suspect you're right. I don't know that Biogen's going to get a ton of sales on the books this year for Aduhelm, certainly not compared to what it will be eventually. The stock has already skyrocketed.

I think you're probably right, Pfizer might have the best shot. It is undervalued and maybe some good news for its COVID vaccine in terms of building investors' confidence in recurring revenue could make that stock go higher.

Orelli: Yeah. Biogen has even said that they don't really expect that much sales from Aduhelm, but I think the initial sales in the first couple of quarters should give an inclination of what the doctors and their patients are thinking about the drug in the long run.

Speights: Right, investors will certainly be reading the tea leaves there.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.